1. Field of the Invention
The technology of the present application generally relates to a system for providing a connecting joint along adjacent joint edges of two building panels. More particularity, the technology provides new and improved connection joints that provide strength and use less material than existing connection joints. Thus, this technology is especially well suited for use in joining thin floor covering panels.
2. Description of Related Art
The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology. The term “plank” is used in a functional sense indicating a generally elongated structural member.
A common type of surface covering is wood flooring. Wood flooring may consist of a plurality of adjacent wooden floor planks affixed to a sub-floor. FIG. 1A shows a cross-section of a wooden floor plank 100, the floor plank may be comprised of a top side 102, a bottom side 104, two edges 106, 108 along the longitudinal sides of the plank, and two ends. The cross-section shown is perpendicular to the two edges and includes a tongue and grove connection joint. The tongue 110 is positioned on a portion of a first edge 106 of a floor plank and the groove 112 is positioned on a second edge 108 of the floor plank. A method of installing floor planks with tongue and groove connection joints includes affixing the tongue side of a first floor plank to a sub-floor 114 with a fastener 116, for example a nail, and positioning the groove side of a second floor plank to receive a portion of the tongue of the first floor plank as is shown in FIG. 1B. In the examples the sub-floor 114 and fastener 116 are shown for illustrative purposes and in practice the sub-floor may be thicker relative to the floor plank 100 than is shown. Further, the fastener may be relatively longer than shown, for example three fifths of the total length of the fastener may be in the sub-floor with two fifths of the length extending through the floor plank. In this method the groove side of the second floor plank is not fastened directly to the sub-floor and is prevented from moving in a vertical direction away from the sub-floor by the tongue of the first floor plank. To create an area of floor covering, this step is repeated with each tongue side of the previously installed floor plank and a groove side of a newly installed floor plank.
Floor planks with tongue and groove connection joints require substantial thickness in order to form a strong joint and a large portion of each floor plank remains as residual waste when the floor plank is replaced. The top portion of the cross-sections of the floor planks in FIG. 1B comprises a wear layer 118 located between the top surface 102 and a bottom portion 120 of the planks. When floor covering is damaged, for example through normal wear and tear, the floor covering is resurfaced using a device such as a sander. Each time the resurfacing process removes about one millimeter of wood material from the top surface of the wear layer 118 creating a new smooth top surface, the overall thicknesses of the wear layer and the plank are reduced. After refinishing the planks several times the wear layer is exhausted leaving only the bottom portion 120 of the planks and an exposed head of the fastener 116, as shown in FIG. 1C. At this point the floor covering needs to be replaced because it can no longer be refinished because no wear layer remains to be resurfaced and further the exposed head of the fastener may damage a resurfacing device. As is shown is FIG. 1C about two thirds of the original plank remains after the wear layer is exhausted and therefore a large portion of the wood of the original floor plank is thrown away. It is therefore desirable to provide surface coverings that use less material to make and have less residual waste.
To manufacture a thin floor plank with a tongue and groove connection joint either, one or more of the tongue, bottom portion of the groove, or top portion of the groove must be made thinner in order to reduce the overall thickness of the floor plank. It is more beneficial to reduce the thickness of the tongue and/or bottom portion of the groove to reduce overall plank thickness because reducing the top portion of the groove will reduce the thickness of the wear layer of the floor plank and therefore reduce the life span of the floor plank. Reducing the thickness of the tongue and/or bottom portion of the groove results in a connection joint that is not a mechanically strong joint because one or more of the tongue, or bottom portion of the groove will be too thin and will become flimsy and likely to crack or break if the joint is stressed. Therefore it is desirable to provide a connection joint that allows overall thickness of the board to be reduced while maintaining a large proportion of wear layer and maintaining a mechanically strong connection joint.
Surface coverings tend to be exposed to changes in temperature and humidity which may affect characteristics of the coverings. For example, wooden surface coverings in a high humidity climate may start to swell and cause cupping or even buckling problems. In a low humidity dry climate wooden floor planks may shrink. Shrinking may cause lateral movements perpendicular to the direction of the grain. Under this condition, in a nail-down application example the un-affixed side of a first plank may move away from an affixed side of a second plank, which results in a lateral separation between the planks. This lateral separation may cause loosening of an un-affixed side of a plank causing a hazard or damage to the floor covering. It is therefore desirable to provide a surface covering with a connection joint that reduces buckling and loosening caused by swelling and shrinking conditions.